title: Accuracy of plateau pressure and stress index to identify injurious ventilation in patients with acute respiratory distress syndrome.
abstract: BACKGROUND
  Guidelines suggest a plateau pressure (PPLAT) of 30 cm H(2)O or less for patients with acute respiratory distress syndrome, but ventilation may still be injurious despite adhering to this guideline. The shape of the curve plotting airway pressure versus time (STRESS INDEX) may identify injurious ventilation. The authors assessed accuracy of PPLAT and STRESS INDEX to identify morphological indexes of injurious ventilation.
  
  
  METHODS
  Indexes of lung aeration (computerized tomography) associated with injurious ventilation were used as a "reference standard." Threshold values of PPLAT and STRESS INDEX were determined assessing the receiver-operating characteristics ("training set," N = 30). Accuracy of these values was assessed in a second group of patients ("validation set," N = 20). PPLAT and STRESS INDEX were partitioned between respiratory system (Pplat,Rs and STRESS INDEX,RS) and lung (PPLAT,L and STRESS INDEX,L; esophageal pressure; "physiological set," N = 50).
  
  
  RESULTS
  Sensitivity and specificity of PPLAT of greater than 30 cm H(2)O were 0.06 (95% CI, 0.002-0.30) and 1.0 (95% CI, 0.87-1.00). PPLAT of greater than 25 cm H(2)O and a STRESS INDEX of greater than 1.05 best identified morphological markers of injurious ventilation. Sensitivity and specificity of these values were 0.75 (95% CI, 0.35-0.97) and 0.75 (95% CI, 0.43-0.95) for PPLAT greater than 25 cm H(2)O versus 0.88 (95% CI, 0.47-1.00) and 0.50 (95% CI, 0.21-0.79) for STRESS INDEX greater than 1.05. Pplat,Rs did not correlate with PPLAT,L (R(2) = 0.0099); STRESS INDEX,RS and STRESS INDEX,L were correlated (R(2) = 0.762).
  
  
  CONCLUSIONS
  The best threshold values for discriminating morphological indexes associated with injurious ventilation were Pplat,Rs greater than 25 cm H(2)O and STRESS INDEX,RS greater than 1.05. Although a substantial discrepancy between Pplat,Rs and PPLAT,L occurs, STRESS INDEX,RS reflects STRESS INDEX,L.
authors.affiliation: * Assistant Professor, † Statistician, § Resident, ** Associate Professor, †† Professor, Dipartimento di Anestesiologia e Rianimazione, Università di Torino, Ospedale S. Giovanni Battista-Molinette, Torino, Italy. ‡ Professor, Keenan Research Center at the Li Ka Shing Knowledge Institute of St. Michael's Hospital; Department of Medicine and Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Ontario, Canada. ‖ Assistant Professor, # Statistician, Sezione di Anestesiologia e Rianimazione, Dipartimento dell'Emergenza e dei Trapianti d'Organo, Università di Bari, Bari, Italy.
authors.forename: Pier Paolo
authors.initials: PP
authors.lastname: Terragni
authors.forename: Claudia
authors.initials: C
authors.lastname: Filippini
authors.forename: Arthur S
authors.initials: AS
authors.lastname: Slutsky
authors.forename: Alberto
authors.initials: A
authors.lastname: Birocco
authors.forename: Tommaso
authors.initials: T
authors.lastname: Tenaglia
authors.forename: Salvatore
authors.initials: S
authors.lastname: Grasso
authors.forename: Tania
authors.initials: T
authors.lastname: Stripoli
authors.forename: Daniela
authors.initials: D
authors.lastname: Pasero
authors.forename: Rosario
authors.initials: R
authors.lastname: Urbino
authors.forename: Vito
authors.initials: V
authors.lastname: Fanelli
authors.forename: Chiara
authors.initials: C
authors.lastname: Faggiano
authors.forename: Luciana
authors.initials: L
authors.lastname: Mascia
authors.forename: V Marco
authors.initials: VM
authors.lastname: Ranieri
mesh_terms: D005260:Female; D006801:Humans; D008168:Lung / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D015203:Reproducibility of Results; D012121:Respiration, Artificial / Q000009:adverse effects* / Q000379:methods; D012128:Respiratory Distress Syndrome / Q000628:therapy*; D015656:Respiratory Mechanics / Q000502:physiology*; D012680:Sensitivity and Specificity; D013312:Stress, Physiological / Q000502:physiology*; D013990:Tidal Volume / Q000502:physiology; D055397:Ventilator-Induced Lung Injury / Q000175:diagnosis* / Q000209:etiology